A vehicle fuel system may include a fuel tank and a carbon canister to process fuel vapors that may be emitted from the fuel tank. A fuel vapor blocking valve may be installed in a passage or conduit that pneumatically couples the fuel tank to the carbon canister and ultimately to the engine air duct, to be ingested and combusted. The fuel vapor blocking valve may be opened to allow fuel vapors to flow from the fuel tank to the carbon canister and on to the engine intake. The fuel vapor blocking valve may be closed during select vehicle operating conditions to prevent vapors from flowing from the fuel tank to the carbon canister. By blocking fuel vapors flowing to the carbon canister, it may be possible to purge the carbon canister of fuel vapors without fuel vapors flowing from the fuel tank disturbing the engine air-fuel ratio. A fuel vapor blocking valve may be configured as a solenoid valve and it may be held normally open via a return spring. The fuel vapor valve may be closed via electrical current passing through the solenoid. However, supplying electrical current to the vapor blocking valve can decrease vehicle fuel economy by consuming charge produced via an alternator. Therefore, it would be desirable to improve vehicle fuel economy via reducing electrical current supplied to the vapor blocking valve.
The inventors herein have recognized the above-mentioned disadvantages and have developed a vapor blocking valve control method, comprising: receiving sensor input to a controller; proportionately adjusting a vapor blocking valve holding current command for a closed vapor blocking valve based on a fuel tank pressure via the controller; and supplying electrical current to a vapor blocking valve in response to the vapor blocking valve current command.
By proportionately adjusting vapor blocking valve electrical current for a closed vapor blocking valve based on fuel tank pressure, it may be possible to provide the technical result of reducing vapor blocking valve electrical current consumption. Pressure within a fuel tank may exert a force on a vapor blocking valve to open or hold closed the vapor blocking valve. Therefore, fuel tank pressure may be a basis for adjusting electrical current supplied to a closed or commanded closed vapor blocking valve. For example, for the case where fuel tank pressure tends to open the VBV, if fuel tank pressure is positive and high, electrical current supplied to the vapor blocking valve may be proportionately increased to keep the vapor blocking valve closed. On the other hand, if fuel tank pressure is negative relative to atmospheric pressure, vapor blocking valve electrical current may be reduced. Reducing vapor blocking valve electrical current may improve vehicle fuel economy by reducing a load an alternator applies to an engine to supply electrical power to the vapor blocking valve.
The present description may provide several advantages. Specifically, the approach may reduce vehicle fuel consumption. Additionally, the approach may reduce system cost by utilizing existing fuel vapor system components. Further, the approach may reduce system complexity by reducing controller electrical connections.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.